This invention relates to circuit breakers, and, more particularly, to a movable contact arm stop that provides a resilient bumper to absorb the opening energy of a movable contact arm.
In typical circuit breakers, one or more springs are employed for maintaining a contact between movable contacts and fixed contacts against magnetic repulsive forces that naturally build up between the contacts. During short circuit occurrences, magnetic repulsive forces are sufficient to accelerate the movable contact arm of a rotary contact assembly at a very high rate of speed. Contact made between the highly accelerated movable contact arm and surfaces on the inside of the rotary contact assembly may cause the movable contact arm to rebound, which can be undesirable.
Prior art designs attempt to reduce the opening energy by slowing down the speed at which the movable contact arm opens. Prior art designs also incorporate catchers and locks to retain the movable contact arms in the open positions. However, such mechanisms are complicated and expensive, and are not completely reliable.
To overcome the above discussed and other disadvantages of the prior art, the present invention provides a circuit breaker cassette comprising a housing having a fixed contact mounted within the housing, and a movable contact mounted on a contact arm. The contact arm is positionable in a closed position and an open position, wherein the contact arm is closed when the movable contact is in contact with said fixed contact. A spring biases the movable contact arm towards the closed position. A kinetic energy-absorbing stop is positioned to absorb kinetic energy of the contact arm resulting from magnetic repulsive forces forcing the movable contact and the fixed contact apart during a short circuit condition. The kinetic energy-absorbing stop comprises a material more resilient than material forming said housing.